Recently, there is an increasing requirement for forming high quality images. To obtain such images, a finer and highly spherical toner needs to be used. Polymer toners can be suitably used as finer and highly spherical toners.
In the image forming apparatuses, excess toner that remains on the surface of a photoconductor after image formation is commonly cleaned with a cleaning means. However, as the toner becomes finer and more spherical, it becomes difficult to clean it. For example, a cleaning blade, which is a commonly used cleaning means, can not properly clean the excess toner. One approach is to more strongly press the cleaning blade against the surface of the photoconductor, however, the photoconductor can get damaged. Another approach is to apply a lubricant on the surface of the photoconductor. However, if the lubricant is not applied uniformly, the quality of the toner image can degrade.
Sometimes both of the above approaches are employed. In that case there can be two options: apply a lubricant first and then clean excess toner, or clean excess toner first and then apply a lubricant. In Japanese Patent Application Laid-Open (JP-A) No. 2001-305907, the applicant of this application has proposed a method of cleaning excess toner first and then applying a lubricant. However, this technique does not take into account a fine, spherical, polymer toner.
Various lubricants have been known. One of them is zinc stearate. It is common to use a solid rod made of zinc stearate, and use a brush roller to scrap zinc stearate from the rod and apply it to the photoconductor. A powdery lubricant can be used instead of a solid bar. However, a powdery lubricant has some disadvantageous. For example, in general, powders are difficult to manufacture and pack. Moreover, powdery lubricants can contaminate the environment.
The amount of lubricant applied also plays an important role. If the lubricant applied is too less, the lubricant may not be applied uniformly, which leads to improper cleaning and wear of the cleaning blade. On the other hand, if the lubricant applied is too much, excess lubricant can make dirty the surface of a charging roller, or even can absorb moisture, which leads to flow of an electrostatic latent image. JP-A No. H10-260614 and JP-A No. 2003-57996 discloses a technique to determine the most appropriate amount of the lubricant.
JP-A No. 2002-244485 describes a method of controlling the application amount of a lubricant based on image data information to improve cleaning capability of polymer toner. This method is the “the application after the cleaning”, but it is different from the present invention in the way to smooth the application amount of the lubricant.
JP-A No. 2000-330443 describes a method of uniformly applying a lubricant to improve cleaning capability of toner. This method is the “the application after the cleaning”, but it is also different from the present invention in the way to smooth the application amount of the lubricant.
JP-A No. 2000-172138 proposes an invention characterized in that an area applied with a lubricant in an axial direction of a photoconductor almost coincides with an area where a cleaning blade contacts the photoconductor. However, this invention is different from the present invention in a point how to configure the lubricant and the cleaning blade, and in another point whether a lubricant smoothing blade is provided.